Category filter in wordpress admin for custom taxonomy

function restrict_books_by_assessment() {
global $typenow;
$post_type = 'assessment'; // change HERE
$taxonomy = 'it-assessment'; // change HERE
if ($typenow == $post_type) {
$selected = isset($_GET[$taxonomy]) ? $_GET[$taxonomy] : '';
$info_taxonomy = get_taxonomy($taxonomy);
wp_dropdown_categories(array(
'show_option_all' => __("Show All {$info_taxonomy->label}"),
'taxonomy' => $taxonomy,
'name' => $taxonomy,
'orderby' => 'name',
'selected' => $selected,
'show_count' => true,
'hide_empty' => true,
));
};
}

add_action('restrict_manage_posts', 'restrict_books_by_assessment');

function convert_id_to_assessment_in_query($query) {
global $pagenow;
$post_type = 'assessment'; // change HERE
$taxonomy = 'it-assessment'; // change HERE
$q_vars = &$query->query_vars;
if ($pagenow == 'edit.php' && isset($q_vars['post_type']) && $q_vars['post_type'] == $post_type && isset($q_vars[$taxonomy]) && is_numeric($q_vars[$taxonomy]) && $q_vars[$taxonomy] != 0) {
$term = get_term_by('id', $q_vars[$taxonomy], $taxonomy);
$q_vars[$taxonomy] = $term->slug;
}
}

add_filter('parse_query', 'convert_id_to_assessment_in_query');